How to disassociate sex from your ex?

Title says it all really! I enjoyed an explorative, active and varied sex life with the ex, so now I find just about anything vaguely sexual to be a painful reminder of her.

All the advice tells me I need to forget about what she meant to me, so any tips on how to do that would be much appreciated. We both grew an incredible amount over the years, so it feels like she will always be a part of my sexuality.